Triorganophosphites of the general structure (R4O)(R5O)P(OR6) and ((R7O)(R8O)PO)nA, where “A” is an optionally substituted or unsubstituted aliphatic, aromatic, or heteroaromatic radical and n is an integer greater than 1, are used in a number of important commercial applications including their use as antioxidants, stabilizers, anti-wear additives and as ligands for various catalytic processes. Generally, triorganophosphites are produced from PX3 (X═Cl, Br, or I) and the corresponding alcohols (ROH). This reaction occurs stepwise by displacement of X with OR. When X is Cl, the process can form phosphorodichloridite (R4O)PCl2 and phosphorochloridite (R4O)(R5O)PCl intermediates, triorganophosphites (R4O)(R5O)P(OR6) and acid HX.
Several methods for making organophosphites, for example those described in Houben-Weyl, Bd. XXII/2 pages 12-17, G. Thieme Verlag, Stuttgart 1964, and supplement E1, pages 413-421 Stuttgart, N.Y. 1982, are known using readily available PCl3 and the corresponding alcohols. The acid HX can be removed by physical separation or by acid-base reaction using organic or inorganic bases. In addition, U.S. Pat. No. 6,069,267, and U.S. Pat. No. 6,031,120 describe the use of triorganoamines to remove HCl followed by water washing at low temperatures to remove the corresponding ammonium hydrochloride salts from the triorganophosphite mixture.
Houben-Weyl, Bd. XXII/2 Chapter I and pages 30-32, G. Thieme Verlag, Stuttgart 1964 teaches that triorganophosphites are easily hydrolyzed in the presence of water, especially in the presence of acidic compounds, to produce one or more of the compounds diorganohydrogenphosphite (R2O)(R3O)POH, organodihydrogenphosphite (R1O)(HO)PO(H), and phosphorous acid H3PO3. Gerard, Hudson and Healy, respectively, (in G. M. Kosolapoff & L. Maier Eds., Organic Phosphorous Compounds, Vol. 5 pages 41-42, Wiley & Sons., New York, 1973; Healy et al. J. Inorg. Nucl. Chem., 1974, 36, 2579) teach that this hydrolysis reaction is autocatalytic due to the acidic properties of diorganohydrogenphosphite (R2O)(R3O)POH, organodihydrogenphosphite (R1O)(OH)PO(H) and H3PO3. Hydrolysis under basic conditions was found to be slower than hydrolysis in the presence of acids (Westheimer et al., J. Amer. Chem. Soc. 1988, 110, 183). Without the removal of these acidic hydrolysis products, as a result of hydrolysis, there can be significant degradation and loss of the triorganophosphite product during downstream processing and storage. In order to at least partially address this effect, U.S. Pat. No. 3,553,298 teaches that nitrogen-containing compound additives such as amines and magnesium oxide can partially stabilize the triorganophosphites by retarding hydrolysis. However, such additives can cause undesirable effects or be incompatible with the use of the triorganophosphites, for example during preparation of a transition metal-triorganophosphite catalyst or catalyst precursor for reactions such as hydrocyanation and hydroformylation, for example. It would, therefore, be desirable to have a method to stabilize triorganophosphites without using additives that may provide undesirable side effects.
U.S. Pat. No. 6,069,267 Example 1 discloses a sequential treatment of a triorganophosphite reaction mixture in an organic solvent with 0.1 N aqueous HCl, 0.1 N aqueous NaOH, followed by distilled water.
U.S. Pat. No. 6,844,289 discloses a process for combining a crude ligand mixture, prepared for example by the process of U.S. Pat. No. 6,069,267, with divalent nickel compounds and reducing agents to produce a catalyst which is a complex of nickel and a bidentate phosphorus compound. This patent discloses that such crude ligand mixture can contain byproducts which may affect the rate of formation of the nickel-containing catalyst. Disclosed therein are treatment methods which include contacting crude ligand mixture with one or more of, for example, a weakly basic organic resin and a two phase solvent system for liquid-liquid extraction. The patent discloses that various treatments of crude ligand may overcome deleterious rate inhibiting effects of byproduct impurities which are present in the crude ligand.